Programmatically add entries to postfix sender_access file.

BlockSpammer.py

#!/usr/bin/env python2

import sys
import smtplib
from subprocess import call

from email.parser import Parser
from email.utils import parseaddr, make_msgid
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart


# BlockSpammer.py <[email protected]>
#
# MIT license.
#
# Receive an message which contains a forwarded message and (optionally) a
# supplied block message.  Parse the forwarded email, extracting recipient and
# a list of email addresses to block.  Update the Postfix configuration to
# block those addresses.  Email the original recipient back, letting her know
# those addresses are in fact blocked.
#
#
# Needs:
#     smtpd_recipient_restrictions =
#         check_recipient_access hash:/etc/postfix/recipient_access
#
# containing minimally:
#     tehblockaddressss@mydomain           FILTER  blockspammer:dummy
#
# and
#     blockspammer     unix  -       n       n       -       -       pipe    flags=D user=someuser   argv=/usr/bin/sudo /path/to/BlockSpammer.py
#
# and 
#     tehblockaddressss needs to be in /etc/postfix/aliases

msg         = Parser().parse(sys.stdin)
msg_from    = msg['From']

# collection of addresses to block
block = set()

# default block message for postfix sender_access REJECT block
block_message = 'blocked'

for part in msg.walk():
    # print part.get_content_type(), '*'*80; print part
    # multiparts are just containers
    if part.get_content_maintype() == 'multipart': continue
    if part.get_content_type() == 'message/rfc822': # it's a forwarded message
        fmsg = part.get_payload()[0]
        # who the forwarded message was ultimately addressed to
        real_recipient = fmsg['Delivered-To']
        for h in ['From', 'Return-Path']:
            a = parseaddr(fmsg[h])[1]
            if a: block.add(a)
        # MUST break so that additional parts sent by the spammer will not be
        # processed.  NB this relies on parts being ordered .... ;[
        break
    else: # it's a message body from me
        # override the default (uh oh, found a spammer we really don't like)
        block_message = part.get_payload()

block = list(block)

# print 'to', real_recipient
# print 'block', list(block)
# print 'message', block_message

# now add to the postfix block list
blocked = []
BLOCKFILE='/etc/postfix/sender_access'
with open(BLOCKFILE, 'a') as blockfile:
    for e in block:
        assert "mydomain" not in e
        # this works with pcre:/ type tables.  change the string format for something else
        blockfile.write('/{}/\t\tREJECT {}.\n'.format(e, block_message))
        blocked.append(e)

# update the postfix map
call(["/usr/bin/postmap", BLOCKFILE])

# reply to the complaining email
outer               = MIMEMultipart("mixed")
rmsg                = MIMEText(
    'blocked:\n\t{}\nmessage:\n\t{}'.format('\n\t'.join(blocked), block_message), "plain")
rmsg["Message-ID"]   = make_msgid()
rmsg["In-Reply-To"]  = fmsg["Message-ID"]
rmsg["References"]   = fmsg["Message-ID"]
rmsg["Subject"]      = "Re: "+ fmsg["Subject"]
rmsg["To"]           = real_recipient
rmsg["From"]         = "tehblockaddressss@mydomain"

outer.attach(rmsg)
outer.attach(fmsg)

s = smtplib.SMTP('localhost')
s.sendmail("me@mydomain", [real_recipient], rmsg.as_string())
s.quit()